Platelets play a key role in hemostasis and function as essential cellular elements for blood to clot. They also play a fundamental role in myocardial infarction, stroke and deep vein thrombosis. Platelets from type-2 diabetics circulate in a partially activated condition, which likely contributes to the diabetic's underlying cardiovascular disease and proinflammatory state. Interestingly, platelets are now also recognized as key regulators of inflammation, due to their release of potent proinflammatory and prothrombotic mediators such as CD40 ligand and thromboxane A2. Our recent work also shows that human platelets, which lack a nucleus, express the transcription factor peroxisome proliferator activated receptor gamma (PPARy), which when exposed to a PPARy ligand, dampens platelet activation. Further interest in platelets arises from the fact that millions of doses of platelets are transfused into patients with cancer, blood diseases, etc. Platelets can be stored for up to five days prior to transfusion. However, this causes a "platelet storage lesion" that includes partial platelet activation and release of bioactive protein mediators that are also transfused. These "proteomic changes" have been poorly characterized and likely mediate/contribute to post-transfusion adverse effects such as fever, heart rate increases and multi-organ failure. Our multidisciplinary team will test the hypothesis that the platelet proteome differs between normal and type-2 diabetics. We will also begin to characterize platelet proteomic changes that occur during the storage period prior to transfusion. Storage of platelets and subsequent proteomic changes may also reflect ongoing partial platelet activation in vivo, such as occurs in type-2 diabetics. Our studies will identify proteins that could be new biomarkers of platelet function abnormalities and/or new therapeutic targets to dampen unwanted platelet activation, both in healthy platelet donors and those platelet donors with asymptomatic platelet-activating diseases, such as type-2 diabetes. Our specific aims are as follows: Aim 1: Characterize the platelet proteome of fresh normal platelets versus tvpe-2 diabetic platelets. Differences in the proteome between normal and type-2 diabetic platelets will be determined using advanced chromatographic separation coupled with high sensitivity mass spectrometry and verified using a battery of complementary approaches. Whole human platelets and purified platelet membranes will be investigated. Aim 2: Determine changes in the normal and type-2 diabetic platelet proteome during storage for transfusion. Changes in the platelet proteome during the storage (up to 5 days) of platelets from normal donors and from newly diagnosed type-2 diabetics will be determined. We will also determine whether potentially deleterious changes in stored platelets can be blocked by PPARy ligands. Overall, our findings will form the foundation for clinical studies to evaluate new biomarkers of platelet function and improve the platelet deterioration that occurs during the storage period prior to transfusion. (End of Abstract)